We describe the architecture of PHAROS (Petabit Highly-Agile Robust Optical System), developed under the DARPA CORONET program. PHAROS provides traffic engineering, resource management and signaling solutions for highly-agile, large-capacity core optical networks. PHAROS technology facilitates rapid configuration of network resources to address dynamic traffic needs in future global military and commercial communications, such as localized surges in capacity requirements that result from military operations. PHAROS technology also scales to support bandwidth-intensive, network-centric, collaborative and distributed computing applications, and accommodates the continued growth of video and biometric data services. © 2009 IEEE.